package WinterVacation.Day9;

public class Num2 {
    public String toLowerCase(String s){
        if(s == null){
            return null;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            char ch = s.charAt(i);
            if(ch >= 'A' && ch <= 'Z'){
                sb.append((char)(ch+32));
            }else{
                sb.append(i);
            }
        }
        return sb.toString();
    }
}
